As they did in Galimoto , Williams and Stock here bring a cultural tradition to life for young readers. The setting is Haiti, zestfully rendered in Stock's brightly hued watercolors. Sasifi carries a basket on her head for the first time as she walks to market with Mama. Tired and hot, the girl longingly watches a passing tap-tap--a covered, festively painted pickup truck carrying marketgoers and their goods. Announcing they do not have enough money to ride the tap-tap, Mama curtly says, ``Perhaps you are not yet big enough to help me on market day.'' Sasifi proves otherwise, competently selling all of their oranges--and collecting the correct amount of money--while Mama goes off to do her marketing. Her reward is her very first ``fine new hat''--and some coins to buy herself a treat. The spirited child passes up the tempting goodies of the bustling marketplace for a ride home in the tap-tap. Children (even those younger than the intended audience) will enjoy the rollicking ride almost as much as Sasifi herself--who learns to ``tap-tap'' on the truck's side when she wants it to stop. Ages 6-9. (Mar.)